Preventing Power Outages

Surge Protection
Surge suppressor or surge protector by definition is an electrical device that protects a computer from spikes and surges on the power line. According to DTE Energy causes of power outages may include storms, accidents, trees, animals, and high power demand. Most computers have some surge suppression built in, but this protection is not always enough. External surge suppressors come in the form of a unit that plugs into the wall, with outlets for several electrical plugs. However, not all outlet strips have surge suppression. Some of the newer surge equipment protects over voltages on AC power lines, Ethernet and telephone lines.

Another example of a surge suppressor might be designed to sit underneath the monitor on the desktop. Surge suppressors are not always reliable, and once the fuse inside the suppressor is blown, surge suppressor no longer protects from a power spike. It may continue to provide power without warning.

Surge suppressors are measured in let-through voltage and in joules. Let-through voltage is the maximum voltage allowed through the suppressor to the device being protected. Joules is a measure of energy, both voltage and current over a one-second interval. The higher the Joules on a surge protector, the better!

“A whole-house surge protection may be purchased and installed on the circuit panel. While this device provides good protection against lightning strikes, this should not be used in place of smaller surge suppression devices at the outlets. Most spikes occur inside the house, already past the whole-house protection device. The best protection is a combination of both the whole-house protection and the protection at the outlet.” -DTE Energy, 2005

Uninterruptible Power Supply (UPS)
UPS by definition is a backup power supply that works when electrical power to the computer is interrupted. There are three different types of UPS’s - standby, inline and line-interactive.

• A standby UPS switches circuits from the AC circuit to the battery-powered circuit.
• The inline UPS continually provides power through the battery-powered circuit, no switching-ensuring continuous power.
• Line interactive (most common) is a variation of the standby UPS that shortens switching time by always keeping the inverter working. An inverter is a device that converts DC to AC. Line interactive also provides Automatic Voltage Regulator (AVR).

“Due to the way electricity is distributed, there may be some interference in your electric service, whether from storms knocking down power lines or other conditions. When this happens, the AC wave coming into your home can be temporarily distorted and may not convert easily into DC. The result may be blinking clocks, static on your stereo, flickering lights, loss of data on your computer, or even burned-out circuit boards.” -DTE Energy, 2005

Nine Power Problems

Total power failure (Blackout)
A total loss of utility power occurs when voltage falls below 80 volts for several cycles or more, and is often caused by uncontrollable events such as lightning strikes, downed power lines, transformer malfunctions, over-demands on the power grid, accidents, weather conditions and natural disasters. Blackouts can cause file/data corruption or loss, hardware or firmware damage, and system lock-ups.

Power sag
A power sag is defined as a drop of at least 10 percent from normal utility line voltage for a half cycle or more, and is caused by various load and switching mechanisms in the utility grid, or can be caused by the equipment itself. While sags will usually only last a few cycles or seconds, the sudden dip in voltage can cause corruption or loss of data, flickering lights, equipment shut-off, or malfunction with automatic shut-off.

Power surge
A power surge is a short-term increase in voltage of 110 percent or more above the nominal supply voltage, and is often caused by large electrical loads turning on and off in the utility grid. The extra heat from high voltage overwhelms and damages circuitry in digital imaging systems. The system may become corrupt or lose data, malfunction, or simply shut off.

Under-voltage (Brownout)
Under-voltage conditions (also known as brownouts) occur when voltage drops 10 percent below normal voltage yet remains above 80 volts (the threshold for power failure). Brownouts may be intentionally induced by the utility for a few minutes or days to conserve power during periods of peak demand, and can cause data loss, corruption and premature hardware failure when the equipment’s internal power supply component draws more current to make up for the drop in voltage.

Over-voltage
Over-voltage is one of the more infrequent power problems that results from increased voltage for a duration of time. Over-voltage can cause extensive hardware damage, including burned-out circuit boards, component stress or loss, memory loss, data loss, and data errors.

Line noise
Electrical line noise is a high frequency waveform caused by Radio Frequency Interference (RFI) or Electromagnetic Interference (EMI). These common interferences in power can be generated by local or remote influences. Equipment such as transmitters, welding devices, printers, lightning, and electrical equipment can generate RFI and EMI conditions. Line noise can cause program failures, data crashes, data corruption or simple keyboard lock-ups.

Frequency variation
Normal alternating current (AC) produces uniform waveforms. When the regular sine-wave frequency pattern of “healthy” AC power is distorted by fast, transient spikes-often from electronic equipment feeding internal noise back into the power line. Power that is delivered with an irregular and abrasive waveform can cause internal system components to degrade and fail. While components are degrading, system technicians may notice a higher incidence of data errors, system and communication lock-ups and resets in the equipment.

Switching transients
Switching transients are extremely brief periods of under- or over-voltage. Damage caused by switching transients occurs in mere nanoseconds, far less time than a sag or spike. Damage may be incurred in both hardware and software, resulting in burned circuitry, component stress or failure, and memory and data losses.

Harmonic distortion
Caused by distortion of the normal line waveform, harmonic distortion is typically transmitted by nonlinear loads, such as from equipment that places on-and-off demands on the power supply. Therefore, harmonic distortions can be caused by everyday equipment found in any commercial setting, such as switch mode power supplies, variable speed motors and drives, pumps, heaters, robotics, copiers, and fax machines-anything with variable power consumption. Harmonic distortions can cause communication errors, overheating, and hardware damage or premature failure.

The Data Center Journal. Jeff Ames. December 13, 2004. Received: 05-23-05.
http://www.datacenterjournal.com/News/Article.asp?article_id=227

Satellite version of Aug. 14, 2003 Black Out.

Allowable Voltage Levels - The American National Standard (C84.1 - 1995)

1. Minimum voltage measured right at the electrical outlet of an appliance.
2. Preferred voltage range measured at the service entrance (billing meter). This includes the voltage range of 5% below and 5% above the nominal service voltage.
3. This is considered an undesirable voltage at the service entrance, but is not low enough or high enough to cause appliance damage. When the voltage is in this range, a high priority is placed on efforts to correct the voltage to within the favorable range. This includes the voltage range of 8.33% below and 5.83% above the nominal service voltage.

Source: DTE Energy, 2005